PV DomU running linux 3.17.3 causing xen-netback fatal error in Dom0

[Anthony Wright <anthony@overnetdata.com>]

We have a 64 bit PV DomU that we recently upgraded from linux 3.3.2 to
3.17.3 running on a 64 bit 3.17.3 Dom0 with Xen 4.4.0.

Shortly after the upgrade we started to lose network connectivity to the
DomU a few times a day that required a reboot to fix. We see nothing in
the xen logs or xl dmesg, but when we looked at the dmesg output we saw
the following output for the two incidents we investigated in detail:

[69332.026586] vif vif-4-0 vif4.0: txreq.offset: 85e, size: 4002, end: 6144
[69332.026607] vif vif-4-0 vif4.0: fatal error; disabling device
[69332.031069] br-default: port 2(vif4.0) entered disabled state


[824365.530740] vif vif-9-0 vif9.0: txreq.offset: a5e, size: 4002, end: 6656
[824365.530748] vif vif-9-0 vif9.0: fatal error; disabling device
[824365.531191] br-default: port 2(vif9.0) entered disabled state

We have a very similar setup running on another machine with a 3.17.3
DomU, 3.17.3 Dom0 and Xen 4.4.0 but we can't reproduce the issue on this
machine. This is a test system rather than a production system so has a
different workload and fewer CPUs.

The piece of code that outputs the error is in
drivers/net/xen-netback/netback.c.

The DomU has 4000MB of RAM and 8 CPUs.

Any ideas?

Thanks,

Anthony.